Phosphorus-based ligands are ubiquitous in catalysis and are used for a number of commercially important chemical transformations. Phosphorus-based ligands commonly used in catalysis include phosphines and phosphites. These ligands include monophosphine and monophosphite ligands, which are compounds that contain a single phosphorus atom that serves as a donor to a transition metal, and bisphosphine, bisphosphite, and bis(phosphorus) ligands, which contain two phosphorus donor atoms and normally form cyclic chelate structures with transition metals.
An industrially important catalytic reaction using phosphorus-based ligands is olefin hydroformylation. Phosphite ligands are particularly good ligands for these reactions. For example, U.S. Pat. 5,235,113 describes a hydroformylation process in which an organic bidentate ligand containing two phosphorus atoms linked with an organic dihydroxyl bridging group is used in a homogeneous hydroformylation catalyst system also comprising rhodium. This patent describes a process for preparing aldehydes by hydroformylation of ethylenically unsaturated organic compounds, for example 1-octene or dimerized butadiene, using the above catalyst system. The use of phosphite ligands with rhodium has been disclosed in the hydroformylation of functionalized ethylenically unsaturated compounds. See for example Cuny et al., J. Am. Chem. Soc., 1993, 115, 2066; U.S. Pat. Nos. 4,769,498, 4,668,651, 4,885,401, 5,113,022, 5,059,710, 5,235,113, 5,264,616, and 4,885,401; and published international applications WO9303839, and WO9518089.
Hydroformylation processes involving organic bidentate ligands containing an aromatic dihydroxyl bridging group and terminal aryl groups bearing heteroatom substituents are described in German Patent Application DE 19717359 A1.
Hydroformylation processes involving organic bidentate ligands containing two trivalent phosphorus atoms, in which the two phosphorous atoms are linked with a 2,2'-dihydroxyl-1,1'-binaphthalene bridging group, are described in U.S. Pat. No. 5,874,641 and the prior art referenced therein. U.S. Pat. No. 5,874,641 describes ligands containing substituents such as esters or ketones on the 3,3'-positions of the 2,2'-dihydroxyl-1,1'-binaphthalene bridging group. Such ligands provide reasonably good selectivity in the hydroformylation of internal olefins to terminal aldehydes.
Although some of these prior art systems involve commercially viable catalysts, there remains a need for even more effective catalyts to achieve even greater commercial potential. An object of this invention is to provide such improved catalysts for hydroformylation.